全文获取类型
收费全文 | 4348篇 |
免费 | 367篇 |
国内免费 | 1篇 |
出版年
2023年 | 20篇 |
2022年 | 60篇 |
2021年 | 109篇 |
2020年 | 59篇 |
2019年 | 104篇 |
2018年 | 100篇 |
2017年 | 96篇 |
2016年 | 149篇 |
2015年 | 248篇 |
2014年 | 255篇 |
2013年 | 284篇 |
2012年 | 366篇 |
2011年 | 362篇 |
2010年 | 202篇 |
2009年 | 195篇 |
2008年 | 248篇 |
2007年 | 277篇 |
2006年 | 226篇 |
2005年 | 217篇 |
2004年 | 167篇 |
2003年 | 202篇 |
2002年 | 177篇 |
2001年 | 44篇 |
2000年 | 23篇 |
1999年 | 34篇 |
1998年 | 43篇 |
1997年 | 31篇 |
1996年 | 24篇 |
1995年 | 19篇 |
1994年 | 27篇 |
1993年 | 30篇 |
1992年 | 21篇 |
1991年 | 18篇 |
1990年 | 16篇 |
1989年 | 14篇 |
1988年 | 22篇 |
1987年 | 20篇 |
1986年 | 17篇 |
1985年 | 25篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1980年 | 8篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1975年 | 10篇 |
1973年 | 8篇 |
1971年 | 11篇 |
1969年 | 9篇 |
1968年 | 12篇 |
1967年 | 13篇 |
排序方式: 共有4716条查询结果,搜索用时 468 毫秒
991.
992.
Study of Plasmodium falciparum DHHC palmitoyl transferases identifies a role for PfDHHC9 in gametocytogenesis
下载免费PDF全文
![点击此处可从《Cellular microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chwen L. Tay Matthew L. Jones Nicola Hodson Michel Theron Jyoti S. Choudhary Julian C. Rayner 《Cellular microbiology》2016,18(11):1596-1610
Palmitoylation is the post‐translational reversible addition of the acyl moiety, palmitate, to cysteine residues of proteins and is involved in regulating protein trafficking, localization, stability and function. The Aspartate‐Histidine‐Histidine‐Cysteine (DHHC) protein family, named for their highly conserved DHHC signature motif, is thought to be responsible for catalysing protein palmitoylation. Palmitoylation is widespread in all eukaryotes, including the malaria parasite, Plasmodium falciparum, where over 400 palmitoylated proteins are present in the asexual intraerythrocytic schizont stage parasites, including proteins involved in key aspects of parasite maturation and development. The P. falciparum genome includes 12 proteins containing the conserved DHHC motif. In this study, we adapted a palmitoyl‐transferase activity assay for use with P. falciparum proteins and demonstrated for the first time that P. falciparum DHHC proteins are responsible for the palmitoylation of P. falciparum substrates. This assay also reveals that multiple DHHCs are capable of palmitoylating the same substrate, indicating functional redundancy at least in vitro. To test whether functional redundancy also exists in vivo, we investigated the endogenous localization and essentiality of a subset of schizont‐expressed PfDHHC proteins. Individual PfDHHC proteins localized to distinct organelles, including parasite‐specific organelles such as the rhoptries and inner membrane complex. Knock‐out studies identified individual DHHCs that may be essential for blood‐stage growth and others that were functionally redundant in the blood stages but may have functions in other stages of parasite development. Supporting this hypothesis, disruption of PfDHHC9 had no effect on blood‐stage growth but reduced the formation of gametocytes, suggesting that this protein could be exploited as a transmission‐blocking target. The localization and stage‐specific expression of the DHHC proteins may be important for regulating their substrate specificity and thus may provide a path for inhibitor development. 相似文献
993.
Andrew J. Dougill Lawrence Akanyang Jeremy S. Perkins Frank D. Eckardt Lindsay C. Stringer Nicola Favretto Julius Atlhopheng Kutlwano Mulale 《African Journal of Ecology》2016,54(1):59-67
Dual‐scale analyses assessing farm‐scale patterns of ecological change and landscape‐scale patterns of change in vegetation cover and animal distribution are presented from ecological transect studies away from waterpoints, regional remotely sensed analysis of vegetation cover and animal numbers across the southern Kalahari, Botswana. Bush encroachment is prevalent in semi‐arid sites where Acacia mellifera Benth. is widespread in communal areas and private ranches, showing that land tenure changes over the last 40 years have not avoided rangeland degradation. Herbaceous cover is dominated in intensively grazed areas by the annual grass Schmidtia kalahariensis Stent and in moderately grazed areas by the perennial grass Eragrostis lehmanniana Nees. Nutritious perennial grass species including Eragrostis pallens Hack. Ex Schinz remain prevalent in Wildlife Management Areas. Other ecological changes include the invasion of the exotic Prosopis glandulosa Torr. and dense stands of Rhigozum trichotomum Kuntze. in the arid southwest. Regional patterns of wildlife species show that the expansion of cattleposts and fenced ranches has led to large areas of low wildlife conservation value even in areas where cattle production is not practiced. Findings show the need for integrated landscape‐scale planning of land use if the ecological value and biodiversity of the southern Kalahari is to be retained. 相似文献
994.
995.
996.
Giuseppina Amodio Emanuele Sasso Chiara D’Ambrosio Andrea Scaloni Ornella Moltedo Silvia Franceschelli Nicola Zambrano Paolo Remondelli 《Cell biology and toxicology》2016,32(4):285-303
Introduction
MicroRNAs (miRs) regulate gene expression to support important physiological functions. Significant evidences suggest that miRs play a crucial role in many pathological events and in the cell response to various stresses.Methods
With the aim to identify new miRs induced by perturbation of intracellular calcium homeostasis, we analysed miR expression profiles of thapsigargin (TG)-treated cells by microarray. In order to identify miR-663a-regulated genes, we evaluated proteomic changes in miR-663a-overexpressing cells by two-dimensional differential in-gel electrophoresis coupled to mass spectrometric identification of the differentially represented proteins. Microarray and proteomic analyses were supported by biochemical validation.Results
Results of microarray revealed 24 differentially expressed miRs; among them, miR-663a turned out to be by ER stress and under the control of the PERK pathway of the unfolded protein response. Proteomic analysis revealed that PLOD3, which is the gene encoding for collagen-modifying lysyl hydroxylase 3 (LH3), is regulated by miR-663a. Luciferase reporter assays demonstrated that miR-663a indeed reduces LH3 expression by targeting to 3′-UTR of PLOD3 mRNA. Interestingly, miR-663a inhibition of LH3 expression generates reduced extracellular accumulation of type IV collagen, thus suggesting the involvement of miR-663a in modulating collagen 4 secretion in physiological conditions and in response to ER stress.Conclusion
The finding of the ER stress-induced PERK-miR-663a pathway may have important implications in the understanding of the molecular mechanisms underlying the function of this miR in normal and/or pathological conditions.997.
Softening the agricultural matrix: a novel agri‐environment scheme that balances habitat restoration and livestock grazing
下载免费PDF全文
![点击此处可从《Restoration Ecology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dean Ansell Graham Fifield Nicola Munro David Freudenberger Philip Gibbons 《Restoration Ecology》2016,24(2):159-164
The loss and degradation of woody vegetation in the agricultural matrix represents a key threat to biodiversity. Strategies for habitat restoration in these landscapes should maximize the biodiversity benefit for each dollar spent in order to achieve the greatest conservation outcomes with scarce funding. To be effective at scale, such strategies also need to account for the opportunity cost of restoration to the farmer. Here, we critique the Whole‐of‐Paddock Rehabilitation program, a novel agri‐environment scheme which seeks to provide a cost‐effective strategy for balancing habitat restoration and livestock grazing. The scheme involves the revegetation of large (minimum 10 ha) fields, designed to maximize biodiversity benefits and minimize costs while allowing for continued agricultural production. The objectives and design of the scheme are outlined, biodiversity and production benefits are discussed, and we contrast its cost‐effectiveness with alternative habitat restoration strategies. Our analysis indicates that this scheme achieves greater restoration outcomes at approximately half the cost of windbreak‐style plantings, the prevailing planting configuration in southeastern Australia, largely due to a focus on larger fields, and the avoidance of fencing costs through the use of existing farm configuration and infrastructure. This emphasis on cost‐effectiveness, the offsetting of opportunity costs through incentive payments, and the use of a planting design that seeks to maximize biodiversity benefits while achieving production benefits to the farmer, has the potential to achieve conservation in productive parts of the agricultural landscape that have traditionally been “off limits” to conservation. 相似文献
998.
Tumour‐associated macrophages correlate with microvascular bed extension in colorectal cancer patients
下载免费PDF全文
![点击此处可从《Journal of cellular and molecular medicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ilaria Marech Michele Ammendola Rosario Sacco Giuseppe Sammarco Valeria Zuccalà Nicola Zizzo Christian Leporini Maria Luposella Rosa Patruno Gianfranco Filippelli Emilio Russo Mariangela Porcelli Cosmo Damiano Gadaleta Giovambattista De Sarro Girolamo Ranieri 《Journal of cellular and molecular medicine》2016,20(7):1373-1380
Tumour‐associated macrophages (TAMs) represent pivotal components of tumour microenvironment promoting angiogenesis, tumour progression and invasion. In colorectal cancer (CRC), there are no conclusive data about the role of TAMs in angiogenesis‐mediated tumour progression. In this study, we aimed to evaluate a correlation between TAMs, TAM immunostained area (TAMIA) microvascular density (MVD), endothelial area (EA) and cancer cells positive to VEGF‐A (CCP‐VEGF‐A) in primary tumour tissue of locally advanced CRC patients undergone to radical surgery. A series of 76 patients with CRC were selected and evaluated by immunohistochemistry and image analysis. An anti‐CD68 antibody was employed to assess TAMs and TAMIA expression, an anti‐CD34 antibody was utilized to detect MVD and EA expression, whereas an anti‐VEGF‐A antibody was used to detect CCP‐VEGF‐A; then, tumour sections were evaluated by image analysis methods. The mean ± S.D. of TAMs, MVD and CCP‐VEGF‐A was 65.58 ± 21.14, 28.53 ± 7.75 and 63% ± 37%, respectively; the mean ± S.D. of TAMIA and EA was 438.37 ± 124.14μ2 and 186.73 ± 67.22μ2, respectively. A significant correlation was found between TAMs, TAMIA, MVD and EA each other (r ranging from 0.69 to 0.84; P ranging from 0.000 to 0.004). The high level of expression of TAMs and TAMIA in tumour tissue and the significant correlation with both MVD and EA illustrate that TAMs could represent a marker that plays an important role in promoting angiogenesis‐mediated CRC. In this context, novel agents killing TAMs might be evaluated in clinical trials as a new anti‐angiogenic approach. 相似文献
999.
A Series of Pyrene‐Substituted Silicon Phthalocyanines as Near‐IR Sensitizers in Organic Ternary Solar Cells
下载免费PDF全文
![点击此处可从《Liver Transplantation》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lili Ke Jie Min Matthias Adam Nicola Gasparini Yi Hou J. Darío Perea Wei Chen Hong Zhang Stefanie Fladischer Anna‐Chiara Sale Erdmann Spiecker Rik R. Tykwinski Christoph J. Brabec Tayebeh Ameri 《Liver Transplantation》2016,6(7)
An attractive method to broaden the absorption bandwidth of polymer/fullerene‐based bulk heterojunction (BHJ) solar cells is to blend near infrared (near‐IR) sensitizers into the host system. Axial substitution of silicon phthalocyanines (Pcs) opens a possibility to modify the chemical, thermodynamic, electronic, and optical properties. Different axial substitutions are already designed to modify the thermodynamic properties of Pcs, but the impact of extending the π‐conjugation of the axial ligand on the opto‐electronic properties, as a function of the length of the alkyl spacer, has not been investigated yet. For this purpose, a novel series of pyrene‐substituted silicon phthalocyanines (SiPc‐Pys) with varying lengths of alkyl chain tethers are synthesized. The UV–vis and external quantum efficiency (EQE) results exhibit an efficient near IR sensitization up to 800 nm, clearly establishing the impact of the pyrene substitution. This yields an increase of over 20% in the short circuit current density (J SC) and over 50% in the power conversion efficiency (PCE) for the dye‐sensitized ternary device. Charge generation, transport properties, and microstructure are studied using different advanced technologies. Remarkably, these results provide guidance for the diverse and judicious selection of dye sensitizers to overcome the absorption limitation and achieve high efficiency ternary solar cells. 相似文献
1000.
Gabriele Giacomo Schiattarella Fabio Cattaneo Gianluigi Pironti Fabio Magliulo Giuseppe Carotenuto Marinella Pirozzi Roman Polishchuk Domenica Borzacchiello Roberta Paolillo Marco Oliveti Nicola Boccella Marisa Avvedimento Maria Sepe Giuseppe Gargiulo Assunta Lombardi Rosa Anna Busiello Bruno Trimarco Giovanni Esposito Antonio Feliciello Cinzia Perrino 《PloS one》2016,11(7)